The present invention is directed to magnetic record members used for the storage of data information. This information is translated into a code, the elements of which are the direction of the magnetization of discrete areas of a magnetic medium. The information is retrieved by readout devices such as magnetic heads, which sense the direction of the magnetization retained in any of these discrete areas. The magnetic record members involved may be those such as tape, disk, drum or other forms which support the magnetic recording medium.
In order to store large quantities of information, the areas storing each element of information must be small. The distinction of the magnetization of one small area of the magnetic medium from that of contiguous areas generally requires that the magnetic sensing device be placed close to the desired element. This necessitates a precisely defined surface geometry. A high retrieval rate demands a high relative velocity between the medium and the read/write head, and this in turn requires precise surface geometry. The greater the quantity of magnetic information that can be readily stored for distinctive output, and the greater the area useful for the storage of the magnetic information, the better the economy and usefulness of the magnetic recording medium. To store the maximum quantity of magnetic information, the magnetic properties of the recording medium must have critical magnetic and geometric characteristics. These properties must be retained while subject to friction in atmospheres which may contain constituents which corrode metals.
Some currently used magnetic disk coatings contain small alumina particles in the coating for the purpose of attaining sufficient durability. However, the alumina lends nonhomogeneity to the coating and results in magnetic defects. Furthermore, some current coatings have intrinsic, binder-related nonuniformities. The new magnetic disk coatings described herein do not contain alumina, and have been developed to minimize all binder-related nonuniformities. A goal of the present invention is to achieve a particulate magnetic coating with sufficient durability, and with significantly decreased magnetic defects as compared to current disks.